Back cross and F2 generation progeny of highly inbred lines of chickens will be blood typed for isoantigens at six blood group loci at which alleles are known to be segregating. These chickens will be wing-web inoculated at six weeks of age with RSV. Each chicken will be subjectively scored for tumor development periodically to 70 days post-inoculation, monitored clinically by the serum blocking test and peripheral lymphocytes will be stained with a fluorochrome stain. The pattern of tumor growth, the outcome of the blocking test and the proportion of lymphocytes which stain with a fluorochrome stain will be associated with one another and with host blood group genotype. The origin and nature of the material coating the lymphocyte, and which hinders its cytotoxic activity, will be studied. BIBLIOGRAPHIC REFERENCES: Corbett, A.C., W.M. Collins and W.R. Dunlop, l975. Effect of regression of Rous Sarcoma tumors upon egg production in an inbred line of White Leghorns Poultry Science, 54:136-179. Collins, W.M., A. C. Corbett and W.R. Dunlop, 1974, Regression incidence of Rous Sarcoma virus-induced wing-web tumors in inbred and outbred chickens and their crosses. Poultry Sci. 53:l9ll-l9l2. (Abst).